A cyclic carbonate is one of important compounds used for many applications as organic solvents, synthetic fiber-processing agents, materials for medicines, cosmetic additives, electrolyte solvents for lithium cells, and further as intermediates for synthesizing alkylene glycols and dialkyl carbonates.
Heretofore, such a cyclic carbonate is synthesized by reacting an epoxide and carbon dioxide in the presence of a homogeneous catalyst under a suitable pressure. As the homogeneous catalyst, halides of alkali metals (Patent Literature 1) and onium salts such as quaternary ammonium salts (Patent Literature 2) are well known for a long time and are used industrially.
However, when such a homogeneous catalyst is used, it generally requires a separation procedure, such as distillation of the catalyst from the reaction mixture. Thus, not only the production process is complicated but also some problems such as degradation of catalyst and formation of byproducts may occur during separation step.